In recent years there has been a growing concern over exposure to toxins in the environment and the food supply. The Federal Water Pollution Control Act Amendments of 1972 (PL 92–500) recognized the need for monitoring and establishing the presence of toxic substances in water. Organic pollutants are frequently present in very small amounts, and often comprise a large number of similar compounds which may have been deposited at a particular location by a variety of means. Some of these pollutants are concentrated in the tissues plants and animals, and can be hazardous to these life forms as well as to the animals, including humans, that eat them. Thus it is important top be able to measure accurately trace amounts of contaminating pollutants.
While conventional chromatography and detection techniques are effective measurers and detectors of organic compounds, the samples to be tested contain the organic compound components in matrices or are in matrices which may interfere with the proper extraction and detection of the compound components to be detected. Using conventional techniques, it has been difficult to determine certain compounds, to assess the degree of matrix effects on compound recovery, and to quantify accurately the amounts of these and other compounds.
Soil, biological samples, oils, and water each present unique difficulties and interfering chemicals. Techniques prior to, and even after, the vacuum extractor described in applicant's earlier U.S. Pat. No. 4,600,599, have not been particularly effective in detecting an accurate amount of chemicals in certain types of samples because of low rates of extraction and poor separation.
Prior investigators have attempted to measure trace organic compounds by a number of techniques. One method is to sample gas from the head space above a sample in a closed container. The gas sample is then injected into a gas chromatograph for measurement. Details and variations on this technique are described in references cited in Hiatt, U.S. Pat. No. 5,411,707, the entire contents of which are hereby incorporated by reference.
Other methods for measuring trace organic chemicals which have not been entirely successful include pentane extraction of organic compounds from fish, or the purge and trap method.
Some of the problems with heating a sample and trapping the released compounds have been ameliorated by using a vacuum rather than heat to extract compounds. Improvements in the purge and trap method have been described by Hiatt in Analytical Chemistry, 55: 506–516 (1983) and Hiatt, U.S. Pat. No. 4,600,599.
Further improvements in these methods are provided in Hiatt, U.S. Pat. No. 5,411,707. This system detects and measures low concentrations of distillable substances using vacuum distillation in which water and other compounds are removed by a condenser, and gases recollected in a cryogenic concentrator connected to at least one gas chromatograph/mass spectrometer or other analytic detector, such as atomic adsorption, HPLC, ICP, SCFE, and the like. This device is capable of analyzing one sample accurately by the standard methods. However, each analysis must be followed by an operator's intervention to remove the sample container holding residue from the distilled sample, and then attaching a new sample for distilling. This one sample at a time process requires an operator to stand by, and therefore, it is not efficient for production analyses.